The present disclosure concerns sensor systems and test rigs comprising sensor systems. More specifically the invention concerns sensors supported in use within fluid flows via masts. The disclosure may have particular application in the field of gas turbine engines where sensors may be supported in an airflow and measurements taken indicative of component and/or system performance during testing and/or operation. The disclosure is not however limited to such applications and it will be appreciated that the disclosure may be applicable to other systems where sensed information is required from a fluid flow region and/or where a mast supporting a sensor is required to pass through a fluid flow region. By way of example the disclosure may be applicable to the taking of sensor measurements via a mast extending into a ducted liquid flow or in any other submerged environment via a mast, antenna, probe or similar. Similarly the disclosure may be applicable where a sensor is positioned on a mast, antenna, probe or similar that is subjected to an air flow.
For convenience the following background is provided in the context of sensors used in gas turbine engines, but this is not intended to be limiting.
When measuring the performance of gas turbine engine components and/or broader systems of the gas turbine engine it is sometimes desirable to take sensor measurements in an airflow region. Such measurements may be taken during rig tests (e.g. to test the performance of a new fan design) or pass of testing, but may also be performed during normal in-service operation (e.g. for engine health monitoring or engine control purposes).
An example of such measurement taking often performed during fan rig testing is the collection of flow velocity and turbulence data downstream of the fan blades. A ‘hot-wire’ anemometer sensor is positioned in the air flow, downstream of the fan blades, via an elongate probe extending through an access opening in a fan case surrounding the fan. The anemometer is used to scan the flow velocity field moving in the blade span-wise direction. The velocity field behind the fan is important for the analysis of fan outlet guide vane and engine section stator interaction noise and performance. The ‘hot-wire’ is exposed to the flow and the resistance of the wire changes due to the convection heat transfer by the flow. It has been found however that vibration and buffeting of the elongate probe adversely impacts on the accuracy of the sensor readings. The motion of the sensor contributes to the flow velocity values measured. The adverse effect increases in severity as a longer length of probe is exposed to the air flow (i.e. as the sensor is moved ever further in towards the roots of the fan blades).